1. Field of the Invention
The present invention relates to a printed circuit board, and more particular relates to a printed circuit board having multiple holes and a design method thereof.
2. Description of Related Art
For the electronic industry, a printed circuit board (PCB board) usually has screw holes used for fixing. The number of the screw holes is one or two. For a better connection with the ground, an inner wall of a standard screw hole is usually coated with a layer of conductive metal material. The layer of conductive metal material is connected with the ground through driving a screw at the screw hole in order to reduce the electrostatic discharge (ESD) and the electromagnetic interference (EMI). Through a proof of an experiment, the drawback of above design is that when driving a screw, the screw may damage the inner wall of the screw hole. Because of the damage of the screw hole, the screw is not fixed well so as to affect the use of a product. In order to improve that phenomenon, when design a PCB, an inner wall of a screw hole may not be coated with a layer of conductive metal material as so to expose the PCB substrate. When a PCB designer performs a design, each actual device on a PCB has to correspond to each device drawn on a circuit diagram. This process is called “DECAL” in the PCB industry. Therefore, before design a PCB, a “DECAL” must be built first in order to start the following process.
Currently, a standard PCB usually includes three or more screw holes. A PCB software can not establish a “DECAL”. At this time, a PCB designer usually enforces a PAD to overlap (a PAD forcedly overlaps a pin of a device). The above design violates the PCB design rule so as to generate a design rule check (DRC) error. The DRC error can not be removed by the PCB software, and can only be ignored by the PCB designer.